[TIL#4] JavaScript 기초-2

Goal: JavaScript 의 기본적인 내용 공부

Table of Contents
1. var, let, const 차이
2. 자바스크립트 데이터 타입
3. 배열의 활용

3.배열의 활용

- 배열 선언 (Declaration)

const arr1 = new Array();
const arr2 = [1, 2];

- Index position

const fruits = ['🍎', '🍌'];
console.log(fruits);
console.log(fruits.length);
console.log(fruits[0]);
console.log(fruits[1]);
console.log(fruits[2]);
console.log(fruits[fruits.length - 1]);
console.clear();

-Looping over an array
print all fruits

• for

for (let i = 0; i < fruits.length; i++) {
  console.log(fruits[i]);
}

• for of

for (let fruit of fruits) {
  console.log(fruit);
}

• forEach

fruits.forEach((fruit) => console.log(fruit));

-Addtion, deletion, copy

• push: add an item to the end

fruits.push('🍓', '🍑');
console.log(fruits);

• pop: remove an item from the end

const poped = fruits.pop();
fruits.pop();
console.log(fruits);

• unshift: add an item to the benigging

fruits.unshift('🍓', '🍋');
console.log(fruits);

• shift: remove an item from the benigging

fruits.shift();
fruits.shift();
console.log(fruits);

note!! shift, unshift are slower than pop, push
splice: remove an item by index position

fruits.push('🍓', '🍑', '🍋');
console.log(fruits);
fruits.splice(1, 1);
console.log(fruits);
fruits.splice(1, 0, '🍏', '🍉');
console.log(fruits);

• combine two arrays

const fruits2 = ['🍐', '🥥'];
const newFruits = fruits.concat(fruits2);
console.log(newFruits);

-Searching

• indexOf: find the index

console.clear();
console.log(fruits);
console.log(fruits.indexOf('🍎'));
console.log(fruits.indexOf('🍉'));
console.log(fruits.indexOf('🥥'));

- includes

console.log(fruits.includes('🍉'));
console.log(fruits.includes('🥥'));

- lastIndexOf

fruits.push('🍎');
console.log(fruits);
console.log(fruits.indexOf('🍎'));
console.log(fruits.lastIndexOf('🥥'));

참고: 드림코딩 by 엘리